When light propagates through a random medium,
scattering reduces
information about whatever lies across the medium and
the electromagnetic field,
composed by many interfering wave modes,
provides a complicated emission pattern
as light undergoes multiple scattering. If enough power is pumped into the medium
multiple scattering may support the population inversion of atoms and molecules above some optical gap, yielding a random laser
[1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}.
Random lasers are made of an optically active
medium and randomly placed scatterers (sometimes both in one [2]}). The first provides the gain, the latter provides the high refraction index and the feedback mechanism needed
to lead to amplification by stimulated emission.
As opposed to ordered standard multimode lasers, random lasers do not require complicated construction and rigid optical alignment, have a low cost, undirectional emissions, high operational flexibility and give rise to a number of promising applications
in the field of speckle-free imaging [15]}, [16]}, granular matter [9]}, [18]}, remote sensing [19]}, [20]}, [12]}, medical diagnostics and biomedical imaging [22]}, [23]}, [24]}, [25]}, [12]}, optical amplification and optoelectronic devices [27]}, [28]}, [12]}.
